Antenna control system and method

ABSTRACT

Each of multiple directional transmissions from an antenna array of a subscriber unit are received at a base unit. Based on the detected quality of received signals at the base unit, directional transmissions from the antenna array that produce a higher quality of received signal at the base unit receiver are identified. Feedback messages can be used to notify the subscriber unit which of the directional transmissions are optimal. Consequently, settings of an antenna array at the subscriber unit can be adjusted to support more efficient directional transmissions from the subscriber unit to the base unit.

RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/250,908 filed on Dec. 1, 2000 entitled “Antenna Power ControlSystem and Method,” and U.S. Provisional Application Ser. No. 60/251,148filed on Dec. 4, 2000 entitled “Antenna Power Control System andMethod,” the entire teachings of both being incorporated herein by thisreference.

BACKGROUND

Precise power control in wireless communication systems such as cellularmobile telephone systems can be problematic, especially at the edge of acell where interference is often the highest. Due to potentialinterference, the benefit of techniques such as high order modulation totransmit at higher data rates can be limited.

Code Division Multiple Access (CDMA) systems such as IS-95 and IS-2000are interference limited, and their inherent capacity generally can beenhanced using beam-steering techniques. For example, based on indoorand outdoor field trials, significant improvements in signal tointerference ratio (SIR) has been achieved using directional antennaarrays.

SUMMARY OF THE INVENTION

One aspect of the present invention is directed toward a system andmethod to increase the bandwidth of a wireless communication system. Inan illustrative embodiment, each of multiple directional transmissionsfrom a transmitter of a subscriber unit is received at a receiver unitsuch as a base unit of a CDMA (Code Division Multiple Access)communication system. A quality of received signals at the receiver unitis then determined for each of the multiple directional transmissionsfrom the transmitter. Based on the detected quality of received signals,the directional transmission from the transmitter that produces a higherquality received signal at the receiver can be identified. More optimalantenna settings of the transmitter can thus be determined by comparinglink quality metrics generated for each of multiple directionaltransmissions. Consequently, settings of the subscriber unit transmittercan be adjusted to support more efficient directional transmissions to abase station receiver.

A link quality message indicating which of multiple directionaltransmissions from the transmitter produces a higher quality receivedsignal can then be communicated to the subscriber unit. This feedbackinformation can be conveyed in a number of ways. For example, a linkquality message can be transmitted to the subscriber units over adedicated, shared channel such as a feedback channel partitioned intoperiodically repeating sequences of frames. In a more specificapplication, feedback messages are communicated to a subscriber unit ona forward link CDMA channel via a technique such as bit-puncturing on anassigned forward link channel.

A link quality message can be a metric based on system parameters. Forinstance, the receiver unit or base unit can measure a power level of areceived signal for each of multiple directional transmissions from thetransmitter of a subscriber unit. Based on received power levels foreach of multiple directional transmissions, a preferred antenna settingfor the subscriber unit and corresponding transmitter can be determined.A link quality message can be based on other suitable system parameterssuch as a signal to noise ratio or bit error rate detected at thereceiver unit.

In one application, a link quality message communicated to a subscriberunit is a single bit indicating which of two previous directionaltransmissions from the subscriber unit produces a higher qualityreceived signal at the base unit. Typically, a subscriber unit issynchronized with the base station for transmitting a majority of datainformation to the base unit based on first directional antenna settingsand occasionally transmitting from the subscriber unit to the base unitbased on second directional antenna settings.

A transmit lobe of the subscriber unit and corresponding wirelesstransmitter can be multiplexed between two or more different angularpositions in a horizontal plane. In this way, the subscriber unit cantransmit along two or more paths, each having a potentially differentpath loss depending on environmental conditions.

If it is determined that new antenna settings of a subscriber unit wouldbe more optimal in lieu of previously used settings, the transmitter orantenna array of the subscriber unit can be adjusted accordingly.Consequently, a beam-steering subscriber unit that is mobile withrespect to a base unit can be adjusted so that a wireless communicationlink is continually optimized for use. The receiver can usebeam-steering techniques to receive a wireless signal.

Link quality messages can be transmitted to corresponding subscriberunits over a dedicated or shared channel. In this instance, a forwardlink channel from the base unit can be partitioned to transmit multiplefeedback messages to each of multiple subscriber units on a forward linkCDMA channel.

Each subscriber unit is optionally assigned use of particular time slotsor data fields of the feedback channel to retrieve feedback messages.Part of a time-slot can be allocated for use by a subscriber unit toreceive feedback messages indicating how to adjust its antenna settings.

Based on these techniques, a base unit can monitor received signals andgenerate feedback information to maintain efficient wireless links witheach of multiple subscriber units.

Another aspect of the present invention involves providing feedbackinformation to one or multiple subscriber units so that theircorresponding transmit settings such as power output levels areminimized for a particular antenna orientation and position in a sharedwireless communication system. For instance, a subscriber unit cantransmit Power Control Groups (PCGs) to the base unit over multiplesuccessive time slots or frames. In this instance, the PCGs can beanalyzed at the base unit for generating feedback information that iscommunicated to the subscriber unit.

A feedback channel from the base unit to the subscriber unit can be usedto adjust power settings of a transmitter at the subscriber unit so thatits data transmissions are optimized. For example, a continuous,periodic or intermittent bit stream can be transmitted on a feedbackchannel to the subscriber unit indicating whether it should increase ordecrease its power output level for future transmissions along aparticular path.

Generally, multiple types of antenna or transmitter settings can beadjusted based on receiving two or more types of feedback messages in afeedback channel. Consequently, two or more feedback control loops canbe supported to adjust directional transmissions of the transmitter.

A single feedback bit such as a power control bit received in thefeedback channel can indicate whether power output at the subscriberunit should be increased or decreased for future transmissions. Thus,for each of multiple framed transmissions from the subscriber unit, apower level can be increased or decreased, for example, by 1 dB. Thepower control bit can be dithered between logic high and logic lowlevels for successive transmissions over the feedback channel so thatthe subscriber unit transmits at an optimal or near-optimal power outputlevel.

In one application, the power control bit is occasionally substitutedwith a lobe compare bit to control a directional output of thetransmitter rather than power output. Accordingly, informationtransmitted in a data field, time slot or frame of the feedback channelcan be used to control multiple aspects of a subscriber unit.

In certain situations, the transmitter settings will be adjusted totransmit along a new direction. Since a path loss can be different forthe new directional transmissions, the power control feedback messagescan then be communicated to readjust a power output of the transmitter.

A specific subscriber unit can identify a type of feedback controlmessage based on a time slot or frame in which it is transmitted. Forexample, a position of a feedback message in a frame of multiplerepeating sequences of frames can be used to identify a type of feedbackmessage received over the feedback channel. No additional data such as atag indicating the type of feedback message is necessary. However, itshould be noted that in one application, a tag or message typeidentifier is used to indicate the type of feedback message rather thanthe position of a frame in a sequence of frames to identify a messagetype. Consequently, a power control loop and lobe control loop can beestablished between a subscriber unit and base unit to optimizetransmitter settings at the subscriber unit.

As discussed, the subscriber unit can occasionally transmit along adifferent direction in a specified time interval, time slot or frame.The base unit can be synchronized to receive the signal along thedifferent direction and, instead of communicating a power control bitback to the subscriber unit in a specified feedback time slot, the basestation can transmit a lobe compare bit in a feedback channel to thesubscriber unit. The lobe compare bit can indicate which transmittersetting at the subscriber unit is perceived to be better for directionaldata transmissions.

A bit or bit sequence in a time slot of a feedback channel can have aunique purpose depending on which time slot or data field it istransmitted. In one application, feedback is provided to control twoaspects of a transmitter. First, messages in the feedback channel can beused to provide feedback information to control transmitter power outputsettings for directional transmissions from a subscriber unit to thebase unit. Second, a bit or sequence of bits in the feedback channel canbe used to identify which of multiple directional settings of thesubscriber unit is optimal for the wireless communication system.Consequently, a two-tiered control loop including multiple types offeedback messages can be used to maintain antenna settings.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1 is a block diagram of a wireless communication system accordingto certain principles of the present invention.

FIG. 2 is a block diagram of a transceiver interface at a subscriberunit according to certain principles of the present invention.

FIG. 3 is a block diagram of a transceiver interface at a base stationaccording to certain principles of the present invention.

FIG. 4 is a diagram illustrating different radiation lobe patternsgenerated by an antenna device according to certain principles of thepresent invention.

FIG. 5 is a timing diagram illustrating a time-slotted forward andreverse link channel supporting feedback according to certain principalsof the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

FIG. 1 is a block diagram illustrating a communication system supportingthe transmission of data information over multiple allocated wirelesscommunication channels according to certain principles of the presentinvention. Users at remote terminals such as personal computer device 12can compete for wireless bandwidth allocation. Hence, it is desirablethat limited resources in wireless communication system 10 are optimizedfor data throughput.

According to the following description, communication system 10 isdescribed as a wireless communication link such as a wireless CDMA (CodeDivision Multiple Access) or other spread spectrum system in which radiochannels are shared among multiple users. However, it should be notedthat the techniques described herein can be applied in any suitableapplication supporting shared access. For example, the principles of thepresent invention can be applied to other types of media such ascellular telephone connections, wireless Local Area Network (LAN)connections, line of sight connections, or other physical media to whichallocation of wireless resources such as data channels are granted on anas-needed basis.

As shown, communication system 10 can include a number of PersonalComputer (PC) devices 12-1, 12-2, . . . 12-h, . . . 12-m, correspondingSubscriber Access Units (SAUs) or terminals 14-1, 14-2, . . . 14-h, . .. 14-m, and associated directional antenna arrays 16-1, 16-2, . . .16-h, . . . 16-m. Centrally located equipment can include base stationantenna array 28, and corresponding base station processor (BSP) 20 andantenna array interface 34. The use of specific types of equipment canvary depending on an application. For example, base station antennaarray 28 and subscriber unit antenna array 16 can include antennadevices, transmitter, receivers, transceivers, dipole antennas, andtransducers that transmit or receive wireless signals.

Generally, base station processor 20 can provide connections to and froma network gateway 22, network 24 such as the Internet, and network fileserver 30. Connectivity can include additional wireless links to supportmultiple logical connections.

In one application, communication system 10 is a demand access, point tomulti-point wireless communication system such that PC devices 12 cantransmit data to and receive data from network server 30 throughbi-directional wireless, logical connections implemented over forwardlinks 40 and reverse links 50. That is, in the point to multi-pointmultiple access wireless communication system 10 as shown, a given basestation processor 20 can support communication with a number ofdifferent subscriber units 14 in a manner which is similar to a cellulartelephone or mobile communication network. Accordingly, system 10 canprovide a framework for a CDMA wireless communication system in whichdigital information is relayed on-demand between multiple mobilecellular users and a hardwired network 24 such as the Internet.

PC devices 12 are typically laptop computers, handheld units,Internet-enabled cellular telephones, Personal Digital Assistant(PDA)-type computers, digital processors or other end user devices,although any suitable type of processing device can be used in place ofPC devices 12.

It should be noted that PC devices 12 need not be terminal devices. Forexample, a subscriber or access unit 14-m can be connected to network 26such as LAN (Local Area Network).

Typically, each PC device 12 is connected to a respective subscriberunit 14 through a suitable wired connection such as an Ethernet-typeconnection or similar cable.

Each subscriber unit 14 can permit its associated PC device 12 access tonetwork file server 30 or other target devices on network 24. In areverse link 50 direction, that is, for data traffic traveling from PCdevice 12 towards server 30, PC device 12 transmits based on a transportprotocol such as an Internet Protocol (IP) level packet to thesubscriber unit 14. One aspect of the transport layer or transportprotocol is to ensure quality of service and accurate delivery ofinformation between logical computer-to-computer connections. In the OSI(Organization for Standardization's Open Systems Interconnection) model,the transport layer is one level above the network layer and is thefourth of seven layers.

In addition to the use of a transport protocol to supportcomputer-to-computer communications, subscriber unit 14 thenencapsulates the wired framing information (i.e., Ethernet framing) withappropriate wireless connection framing that is used to frameinformation for transmissions over wireless reverse link 50. In otherwords, data packets are split, combined, or rebundled for transmissionover the wireless link.

After the information is framed, the appropriately formatted wirelessdata packets then travel over one of the radio channels that comprisereverse link 50 through antennas 16 and 28. At the central base stationlocation, base station processor 20 and antenna array interface thenextract the radio link framed data packets and reformats the packetsinto an original or near original IP format. The packets can then besubsequently routed through gateway 22 and any number or type ofnetworks 24 to an ultimate destination such as a network file server 30.Accordingly, network data messages can be packed for transmission over awireless link and unpacked for transmission over a wired or opticalnetwork.

In one application, information generated by PC devices 12 are based ona TCP/IP protocol. Consequently, PC devices 12 can have access todigital information such as web pages available on the Internet.

It should be noted that other types of digital information can betransmitted over radio channels or sub-channels of communication system10 based on the principles of the present invention. More specifically,the data information can be any type of data information encapsulatedusing a suitable network protocol.

Data can also be transmitted from network file server 30 to PCs 12 onforward link 40. In this instance, network data such as an InternetProtocol (IP) packets originating at file server 30 travel on network 24through gateway 22 to eventually arrive at base station processor 20. Ina similar manner as discussed, appropriate wireless protocol framing canthen be added to raw data such as IP packets for communication of thepackets over a wireless forward link 40. Modulation and up-convertercircuits can be employed to produce a signal suitable for radiotransmission on one or more forward link traffic channels 42.

The newly framed packets travel through base unit 18 and antenna array16 to the intended receiver subscriber unit 14. An appropriate targetsubscriber unit 14 demodulates and decodes the radio signal or signalsto receive the wireless packet formatting layer, and forwards the packetor data packets to the intended PC device 12 that performs IP layerprocessing. It should be noted that subscriber unit 14-m can be coupledto another network such as network 26 as shown.

A given PC device 12 and file server 30 can therefore be viewed as theend points of a duplex connection at the IP level.

Once a connection is established between base station processor 20 and acorresponding subscriber unit 14, a user at PC device 12 can transmitdata to and receive data from file server 30 on an as-needed basis. Morespecifically, one or multiple channels can be allocated to each ofmultiple users on an as-needed basis to transmit at higher data rates.

Reverse link 50 optionally includes different types of logical and/orphysical radio channels such as access channel 51, multiple trafficchannels 52-1, . . . 52-m, and maintenance channel 53.

A combination of these channels can be used to maintain one or multiplewireless links. Reverse link access channel 51 can be used by thesubscriber units 14 to send messages to base station processor 20 andrequest that traffic channels be granted to them. For example, trafficchannels carrying data packets can be assigned or reallocated to one ormultiple users on an as-needed basis. Assigned traffic channels 52 thencarry payload data from subscriber unit 14 to base station processor 20.Notably, a given connection can have more than one traffic channel 52assigned to it.

Maintenance channel 53 can also carry information such assynchronization and power control messages to further supporttransmission of information over both the reverse link 50 and forwardlink 40.

In a similar manner, the forward link 40 can include a paging channel41, which is used by base station processor 20 to inform a subscriberunit 14 of general information such as that one or multiple forward linktraffic channels 52 have been allocated or assigned to it for thetransmission of data. Additionally, the channel can be used to informsubscriber units 14 of allocated or assigned traffic channels 52 in thereverse link direction.

Traffic channels 42-1 . . . 42-n on forward link 40 can be used to carrypayload information from base station processor 20 to subscriber units14. Additionally, maintenance channels can carry synchronization andpower control information on forward link 40 from base station processor20 to subscriber units 14.

Traffic channels 42 on forward link 40 can be shared based on a TimeDivision Multiplexing scheme among multiple subscriber units 14.Specifically, a forward link traffic channel 42 can be partitioned intoa predetermined number of periodically repeating time slots fortransmission of data packets to multiple subscriber units 14.

It should be noted that a given subscriber unit 14 can have, at anyinstant in time, multiple time slots or no time slots of a wirelesschannel assigned to it for use. However, in certain applications, anentire time-slotted forward or reverse link traffic channel can beassigned for use by a particular subscriber unit 16. Consequently,multiple subscriber units 14 sharing wireless resources can transmitshort bursts of sporadically generated data at high throughput rates.

Base station 18 includes antenna array 28 that can be used inconjunction with antenna array interface 34 for detecting the receivedsignal quality level of reverse link directional transmissions fromcorresponding antenna arrays 16 coupled to subscriber units 14.

Antenna array 16 coupled to corresponding subscriber units 14 can besteerable so that a radiation pattern from a subscriber unit 14 can bedirected towards a particular target such as base unit 18 and, morespecifically antenna array 28.

Additionally, directional transmissions from antenna array 16 can varydepending on a time slot of a channel in which it is transmitted. Thatis, a transmitter can transmit a wireless signal in a first directionfor one time slot and transmit in a second direction for another timeslot.

Implementations of directional antenna systems are described inco-pending U.S. patent application entitled “A Method of Use for anAdaptive Antenna in Same Frequency Networks” Ser. No. 09/579,084 filedon May 25, 2000, and U.S. patent application entitled “Adaptive Antennafor Use in Wireless Communication Systems” Ser. No. 09/859,001 filed onMay 16, 2001 the entire teachings of which are incorporated herein bythis reference. Generally, any directional antenna array or transducerdevice can be advantageously employed to transmit and receive wirelesssignals according to certain principles of the present invention.

Since multiple users can be assigned CDMA channels on the samefrequency, typically there is interference among users competing foravailable wireless bandwidth. For example, two different subscriberunits 16 can transmit information over a reverse link channel to baseunit 18 from the same general direction. Thus, a signal from asubscriber unit 14 can appear as noise to another subscriber unit 14when such channels are generated onto the same carrier frequency, butusing different coded channels.

Certain aspects of antenna array 16 can be controlled to reduceinterference between adjacently transmitting subscriber units 14 toincrease the overall bandwidth of wireless communication system 10. Forexample, the shape of the radiation pattern of antenna array 16 and itspower output level can be optimized for a particular application. Morespecifically, directional transmissions from antenna array 16 can beadjusted so that the output beam or lobe is wider or narrower.

Additionally, the power output level at which the data is transmitted onreverse link 50 from antenna array 16 can be controlled so that acorresponding wireless signal in the reverse link can be detected bybase unit 18, but not at such a high power transmit level that it causesunnecessary interference with other users. Typically, there is anoptimal signal-to-noise ratio for a given reverse link channel thatresults in maximum throughput of communication system 10 and reductionof overall power consumption by subscriber unit 14. Reduced powerconsumption can be particularly important in applications wheresubscriber units 14 and related equipment such as computer devices 12are powered by a finite power source such as a battery. Generally,aspects of the present invention can be employed so that a power sourcelasts longer.

FIG. 2 is a block diagram of an antenna array and correspondinginterface to transmit and receive a wireless signal from a subscriberunit according to certain principles of the present invention.

As shown, antenna array 16 is controlled by array controller 275 tosteer a transmit or receive beam. Consequently, antenna array 16 cansteer the directionality and coverage area of output beam 296.

Antenna array 16 can be coupled to antenna array interface 15 via acable or it is optionally integrated with interface 15 as a single unit.Likewise a corresponding subscriber unit 14 can be connected to antennaarray interface 15 via a cable or the combination of subscriber unit 14and interface 15 optionally integrated as a single unit.

The power level of output beam 296 can be controlled by adjusting RFamplifier 210. Generally, processor 270 generates control signals toadjust RF amplifier 210 and corresponding output beam 296.

In a transmit mode, data information from subscriber unit 14 is fed intoframer 240 where it is framed with a protocol for transmission over awireless link as discussed. The framed data is in turn is fed tomodulator 230 for modulation of data onto a carrier frequency.Modulation can be any suitable type such as BPSK (Binary Phase ShiftKeying), QPSK (Quadrature Phase Shift Keying), 8-psk, up to n-psk.

Modulated signals generated by modulator 230 are then fed to RFconverter 220 that, in combination with RF amplifier 210, drive antennaarray 16. RF amplifier 210 is adjustable so that a power level of outputbeam 296 can be controlled based on input from processor 270.

Antenna array interface 15 can be adjusted for receiving wireless datainformation from base unit 18. RF detector 245 detects the presence of areceived RF signal. Power level detector 265 can be used to detect apower level of the received signal. Output information generated bypower level detector 265 can be analyzed by processor 270.

As depicted in the block diagram, RF down converter 250 converts thereceived signal and feeds the signal to demodulator 255. The signal isthen demodulated and decoded by de-framer 260 to retrieve packaged datainformation that is eventually reformatted and forwarded to subscriberunit 14.

More details of wireless transmitter and receiver circuits can be foundin U.S. application Ser. No. 09/775,304 entitled “Alternate Channel forCarrying Selected Message Types” filed on Feb. 1, 2001, the teachings ofwhich are incorporated herein by reference.

FIG. 3 is a block diagram of an antenna array and correspondinginterface to transmit and receive wireless signals from a base unitaccording to certain principles of the present invention.

As shown, antenna array interface 34 can include similar circuitry andfunctionality as that described in FIG. 2 for transmitting and receivingwireless signals. More details regarding how base unit 18 communicateswith subscriber unit 14 will be described later in this specification.

FIG. 4 is a top view diagram of exemplary radiation patterns produced bya corresponding directional antenna array according to certainprinciples of the present invention. As shown, subscriber unit 14-1 andantenna array interface 15-1 control a receive or transmit radiationpattern of antenna array 16-1 directed towards base unit 18. In thisinstance, both lobes A and B can be used to transmit information to baseunit 18, although base unit 18 is near the edge of lobe A and,therefore, is almost out of receiving range. If antenna array 16-1happened to rotate an appreciable amount in a counter clockwisedirection from the top view as shown, lobe A would no longer be receivedat base unit 18. In this latter instance, a transmit lobe may not bedetectable at base unit 18 due to its directionality or low powertransmit level at a particular point on the lobe.

As previously discussed, one aspect of the radiation output pattern 296of transmitter or antenna array 16 involves controlling a direction of alobe while another aspect involves controlling its power output level.Lobe A illustrates that antenna array 16 needlessly transmits extrapower to base unit 18, potentially causing unnecessary interference toother subscriber units 14-2, . . . 14-m. Interference can be exacerbatedwhen a subscriber unit 14 is at the edge of a cell. Generally, basestation 18 can receive corresponding reverse link 50 data transmissionsfrom antenna array 16-1 at the side of lobe A. Comparatively, lobe B isapproximately centered so that base unit 18 can receive the reverse linksignal even if the power output level of lobe B were reduced.

Although antenna array 16-1 can be controlled to transmit a wirelesssignal in different directions such as that shown by lobe A and lobe B,antenna array 16-1 can be designed to transmit along any verticaldirection as well as horizontal direction. In one application, antennaarray 16-1 transmits a directional beam using beam-steering techniques.Accordingly, communication system 10 can support more efficientcommunication between subscriber units 14 and base station 18 no mattertheir position in 3-dimensional space.

FIG. 5 is a diagram illustrating message frame information for reverseand forward link channels according to certain principles of the presentinvention. As shown, forward link frames are offset in time byround-trip delay Δt. Generally, a signal is transmitted from antennaarray 16 to antenna array 28 or generally base unit 18 in a time frame215 of reverse link channel 232. A quality of received signal can beanalyzed at base unit 18 to provide feedback information to transmittingantenna array 16. For example, feedback messages can be transmitted inthe opposite direction on forward link 40 and, more specifically,feedback channel 230 to one or multiple subscriber units 14.

According to one aspect of the present invention as mentioned, anoptimal directional transmission from a subscriber unit 14 andcorresponding antenna array 16 can be determined so that datainformation can be efficiently transmitted on the reverse link 50without causing undue noise interference to other subscribers 14-2 . . .14-m or yet other subscriber units in different cells. This technique ofoptimizing the use of particular antenna arrays 16 of correspondingsubscriber units 14 can include adjusting both the power level anddirectionality of a corresponding output from an antenna array 16.

Notably, a path loss between base unit 18 and subscriber unit 14 canvary depending on directionality of antenna array 16. Thus, shifting adirection of a transmitting lobe of a single antenna array 16 for futuredirectional transmissions can result in a power savings since the powertransmission level of other subscriber units 14 can then be reduced as aresult of reduced interference. The power transmission level of reverselinks can also be increased if a signal is not detected. Consequently,communication system 10 can support more robust communications betweenone or multiple base stations and multiple subscriber units 14.

As previously mentioned, another aspect of the present inventioninvolves adjusting a power level of the signals transmitted by antennaarray 16. Reverse link slotted channel 232 of an exemplary reverse linkchannel 50 can include periodically repeating time slotted messages inwhich information is transmitted on reverse link 50 to base unit 18 and,more specifically, to antenna array 28.

As previously discussed, the information transmitted from a subscriberunit 14 can be rebundled network messages. As shown, time-slots orsequence of frames 0-15 can periodically repeat every 20 ms. Each of the16 frames or 16 PCGs (Power Control Groups) is preferably 1.25 mS(milliseconds) in duration. This can vary depending on the application.

Generally, reverse link slotted channel 232 can be any suitable,partitioned reverse link channel 50 such as those previously discussed.Similarly, feedback channel 230 can be a shared or dedicated channel fortransmitting feedback messages from base unit 18 to one or multiplesubscriber units 14.

As its name suggests, frame reference numeral 215 indicates the numberof a time slot in a given cycle of 16 PCGs as shown. Circled letter 210indicates the lobe over which information is transmitted in thatparticular time frame from subscriber unit 14-1 over antenna array 16-1to base unit 18 as shown in FIG. 2. For example, antenna array 16-1 cantransmit information over a reverse link channel to base unit 18 usinglobe A for each of frames 0-14. Antenna device 16-1 can then alter itsdirectional transmissions to transmit information over the reverse linkchannel using lobe B during frame 15. In this way, subscriber unit 14-1multiplexes its directional transmissions to base unit 18 usingdifferent directional lobe patterns.

It should be noted that this method of multiplexing can be expanded sothat antenna array 16 multiplexes its data transmissions along anynumber of lobes or directions. In other words, a subscriber unit 14 canutilize a scanning technique to identify which of multiple directionaltransmissions are optimal.

Since base unit 18 and subscriber unit 16-1 are synchronized withrespect to each other for receiving transmitted data in either thereverse or forward link direction, power level detector 365 at base unit18 can be used to measure a power level of a received signal at antennaarray 28 for a given time frame as transmitted by antenna device 16-1.Subsequently, a message can be transmitted from antenna array 28 tosubscriber unit 14-1 regarding the power level measurement. In this way,feedback information can be provided by base unit 18 to a correspondingsubscriber unit 14.

It should be noted that occasional, newly directed data transmissionsfrom multiple subscriber units 14 can be offset in time from each otherso that communication system 10 does not experience a sudden change ininterference levels that may otherwise result if multiple subscriberunits 14 simultaneously transmit in new directions at the same time.

Referring again to FIGS. 2-5 subscriber unit 14 generates a wirelesssignal to base unit 18 in reverse link slotted channel 232. Processor270 of antenna array interface 15 drives array controller 275 to adjustthe antenna array settings for each frame or time slot. For example,array controller 275 adjusts the settings of antenna array 16 so that ittransmits output beam Lobe A for time slots 0-14 and output beam Lobe Bfor time slot 15.

In this instance, the output signal transmitted by antenna array 16 isreceived at base unit antenna array 28. The received signal is processedand decoded as previously discussed. A quality of received signal duringeach time frame can be determined by detecting a power level of thereceived signal via power level detector 365.

As previously discussed, the quality of received signal also can bequantified based on a bit error rate or signal-to-noise ratio. Based onthe quality of received signal, processor 370 generates a feedbackmessage that is transmitted to subscriber unit 14 over feedback channel230.

One type of feedback message is a power control message. For example, aPower Control Bit (PCB) 220 is transmitted from base unit 18. Generally,subscriber unit 14 transmits over Lobe A to base unit 18, which thendetects a quality of received signal as discussed. Processor 370 in baseunit 18 then compares the detected link quality of received signal to athreshold. If the quality of received signal is below the threshold, aPCB 220 such as a logic ‘1’ is transmitted from the base unit infeedback channel 230 to indicate that subscriber unit 14 should increaseits power output level for successive transmissions. Conversely, if aquality or power level of a received signal is higher than thethreshold, processor 370 can generate a PCB 220 feedback message at alogic ‘0’ indicating that subscriber unit 14 should decrease its poweroutput level for successive transmissions. Thresholds are chosen so thatuse of resources in communication system 10 are optimized for multipleusers.

In this way, the power transmission level can be controlled via thefeedback information transmitted to the base unit 18 over the forwardlink channel. More specifically, successive packets of Power Control Bit(PCB) 220 information can be transmitted to a corresponding subscriberunit 14 to indicate whether to increase or decrease its powertransmission level. Thus, a power level output of antenna array 16 canbe adjusted to account for changes in the immediate environment and pathloss. For example, a new subscriber may begin transmitting informationin the immediate vicinity, increasing the noise level in the area. Inthis instance, subscriber unit 14 may need to increase its power outputlevel to maintain a wireless link with base unit 18. In othersituations, a path loss for a particular lobe may change depending onweather conditions or movement of a subscriber unit 14.

Power Control Bit (PCB) 220 can indicate that the subscriber unit 14-1should increase or decrease its power output level by a specified amountsuch as one dB, depending on the state of the bit. For example, a logic“1” can indicate to increase the power output level of antenna array16-1 while a logic “0” can indicate to decrease its power output level.In this way, the power output level of antenna array 16-1 can beoptimized so that it does not needlessly transmit at excessive levels,which could appear as interfering noise to other channels.

It should be noted that power control bit 220 as transmitted in aforward link channel to a corresponding subscriber unit 14 is typicallydelayed since it can take time to process the received reverse linksignal at base unit 18 and make a determination whether thecorresponding subscriber unit 14-1 should increase or decrease its powerlevel output. As shown in FIG. 5, power control bit 220 in frame 14 offeedback channel 230 as transmitted by base unit 18 is a feedbackmessage based on a previous power measurement of the reverse linkslotted channel 232 transmitted from a subscriber unit 14 during frame12. The amount of such a delay can vary depending on the application.

A particular metric reflecting the power output level of transmittingantenna array 16-1 can be based on one or multiple parameters. Forexample, the metric can be based on a link quality measurement such asbit error rate or signal-to-noise ratio of a selected reverse linkchannel, or both. Generally, any suitable metric reflecting link qualitycan be used to generate feedback information to subscriber unit 14.

Antenna array 16-1 can multiplex transmissions in different directionssuch as along lobe A and lobe B to transmit during a reverse link frame.As shown, subscriber unit 14-1 transmits information in the selectedreverse link channel through lobe B in frame 15 of the reverse linkchannel. Prior to transmission of data along lobe B during frame 15,data from subscriber unit 14-1 on the reverse link channel can betransmitted along lobe A for each of multiple frames 0-14. This 15:1multiplexing ratio is merely exemplary and can modified depending on theapplication.

Feedback information transmitted on feedback channel 230 is received atsubscriber unit 14 and, specifically, antenna array 16. The message isprocessed by processor 270 that, in turn, uses the feedback message toadjust aspects of antenna array 16. For example, based on feedbackmessages, processor 270 can generate control commands to adjust RFamplifier 210 and the power output level of subscriber unit 14.

Typically, the power output for data transmissions using lobe A and lobeB are equal or within 1 dB of each other. Similar to previous reverselink transmissions for frames 0-14, the power level or other suitablelink quality metric of the received reverse link signal for the durationof frame 15 is measured at base unit 18. More specifically, signalstransmitted by subscriber unit 14 in time slots of the reverse linkslotted channel 232 can be received at base unit 18. As discussed thelink quality of the received signal at base unit 18 can be detected bypower level detector 365 or determined by a bit error rate of receivedsignal data. Based on calculated link quality and a comparison of thereceived signal for previous lobe transmissions, processor 370 cangenerate feedback information that is transmitted to the subscriber unit14 indicating which previous directional transmission from subscriberunit 14 produces a high quality received signal. In one application, anactual link quality metric calculated at base station 18 is communicatedto subscriber unit 14 over a wireless channel.

Instead of processing a power measurement to generate a power controlbit 220 and transmitting the power control bit 220 to a subscriber unit14-1 in the feedback channel 230, base unit 18 can analyze a receivedsignal for a new directional transmission and generate a lobe comparebit (LCB) 225 that is transmitted in forward link slot #1. As discussedfor PCB bit 220, LCB bit 225 in forward link frame 1 is delayed so thatbase unit 18 can process information received in reverse link frame 15.A position of the frame in a sequence of periodically repeating framescan be used to identify the type of feedback message received.

Lobe compare bit 225 can provide a relative indication of the receivedpower level or link quality on the reverse link channel 232 for multipledirectional transmissions such as successive frames 14 and 15. Forexample, base unit 18 and, more specifically, antenna array interface 15can separately measure a received link quality of reverse link channel232 for frame 14 and, thereafter, frame 15. These link qualitymeasurements for different lobe transmissions can be compared to eachother by processor 370 to generate the lobe compare bit (LCB) 225. Thus,LCB bit 225 can be used to indicate which of the lobes, A or B, providesa stronger signal or better link quality. A logic “1” transmitted infeedback channel 230 can indicate that lobe B has a greater receivedpower level than lobe A, while a logic “0” can indicate that lobe B hasa lower received power level than lobe A. Thus, a correspondingsubscriber unit 14 can be notified via feedback messages in the forwardlink channel which of multiple directional transmission of antennadevice 16-1 is optimal for use. A subscriber unit 14 can then adjust itsdirectional transmissions based on the LCB bit 225. More specifically,received feedback information can be used by processor 270 to generatecommands that are in turn used by array controller 275 to adjustdirectional output beam 296 from antenna array 16.

Subscriber unit 14 or base station 18 can determine in which directionthe occasional new lobe will be directed based on past experience andinformation stored in memory. Base unit 18 can send a message to baseunit 18 indicating an experimental directional lobe or general antennasettings that are to be used for future directional transmissions.

As discussed, lobe compare bit 225 can be transmitted to a subscriberunit 16-1 in lieu of the power control bit 220 as transmitted inprevious frames. Based on this method of providing dual-mode feedback,subscriber unit 14-1 can be notified which directional transmissions onantenna array 16-1 are optimal and, in addition, how the power outputlevel of the antenna device 16-1 should be adjusted to maintain a linkbetween the subscriber unit 14-1 and base unit 18. Future directionaltransmissions from antenna array 16-1 therefore can be based on lobe Bwhen it is a more optimal path. Accordingly, when lobe B becomes themain transmission direction, its power level can be reduced via thepower control bit 220 as previously discussed so that its output isoptimized for system 10.

It should be noted that functionality provided by antenna arrayinterface 15 can be duplicated in base unit 18 so that correspondingdirectional transmissions from the base unit 18 can be adjusted andmonitored in a similar, but reverse manner as that previously discussed.

Directional transmissions based on multiplexing between lobes can beperformed to sample potentially better wireless transmission paths tobase unit 18. For example, alternate paths from subscriber unit 14-1 tobase unit 18 can be tested periodically or intermittently whether theyhave a lower path loss and would otherwise support data transmissions atlower power levels.

In certain applications, power control bit 220 and lobe compare bit 225information are transmitted to subscriber unit 14-1 via bit-puncturingon a corresponding assigned forward link traffic channel. Alternatively,each subscriber unit 14 can be assigned a time-slot or a data field ofrepeating time slots of a dedicated forward link CDMA channel to receivethe power control bit 220 and lobe compare bit 225. Feedback messagesare optimally tagged to identify their type.

According to other aspects of the present invention, multiple additionallobe positions can be compared with a base lobe setting, such as lobe A,to determine which of multiple possible directional antenna settings isoptimal for subscriber unit 14-1 and communication system 10. Forexample, subscriber unit 14-1 can be set to transmit data on baselinelobe A from subscriber unit 14-1 to base unit 18. A received power levelfor lobe A and lobe B data transmissions can be compared as previouslymentioned to determine which path or lobe provides a more optimal linkbetween subscriber unit 14-1 and base unit 18. Other lobe settings suchas lobe B, lobe C, lobe D and so on can be compared to baseline settingof lobe A to determine which if any of the new possible lobe settingscan be used to transmit data more efficiently to base unit 18. It isanticipated, at least at times, that the power transmit level of aparticular subscriber unit 14 can be reduced based on a new directionalantenna setting. Accordingly, a new antenna setting can account for achanging position of a user or antenna array with respect to base unit18 so that a wireless link is constantly maintained.

In a manner as previously mentioned, the additional power level compareinformation for multiple possible antenna or lobe settings can betransmitted to subscriber unit 14-1. Lobe compare bits 225 for multiplepossible new antenna settings can be used by subscriber unit 14 todetermine an optimal antenna setting on which information shall betransmitted to base unit 18.

Based on a comparison of multiple potential antenna settings with thebaseline settings such as lobe A, subscriber unit 14-1 can optionallytransmit information in a new direction or at a new power output level.Accordingly, a more precise determination as to which of the multiplelobe settings is optimal can be made prior to transmitting informationon a new lobe setting. More specifically, multiple possible antennasettings can be considered before actually transmitting informationbased on a new setting. Two lobe settings such as lobe B and lobe C canbe compared in multiple 20 mS cycles to determine which of the twoantenna settings shall eventually be used to transmit data to base unit18.

It should be noted that subscriber unit 14-1 can monitor multiple lobecompare bits 225 for two or more potential lobe settings before changingfrom one lobe setting to another. This ensures that the lobe settingsare not changed unnecessarily. Consider a situation where a baselinelobe setting is unusually noisy for a short period of time. Forinstance, a lobe compare bit may erroneously indicate that one lobesetting is better than another due to sporadic noise on a particularfrequency channel even though such a channel otherwise generallyprovides a good link between subscriber unit 14-1 and base unit 18. Inthis instance, it may not be desirable to switch to a new lobe settinguntil it is reasonably certain that the new lobe setting can sustaincontinued communications between the subscriber unit 14-1 and base unit18 and that the new lobe setting is more optimal for futurecommunications. A new lobe setting may unnecessarily interfere withanother user.

When transmissions from a subscriber unit 14-1 in the reverse link willbe switched to a new lobe setting, a message can be sent from thesubscriber unit 14-1 to base unit 18 indicating these and other newantenna settings. In this way, base unit 18 can be apprised of thedifferent lobe settings upon which information is transmitted fromsubscriber unit 14-1 to base unit 18. Thus, base unit 18 can keep trackof the antenna array settings of various subscriber units 14 incommunication system 10.

In one application, base unit 18 rather than individual subscriber units14 determine how to set antenna parameters for directional transmissionsof each of multiple subscriber units 14. For example, based upon thelobe compare information, base unit 18 can transmit a message to thecorresponding subscriber unit 14 indicating an antenna setting that isto be used for transmitting data in the reverse link. In this way, asingle central tracking unit and controller located at base unit 18 candetermine antenna settings for multiple subscriber units 14 to optimizea use of wireless resources of communication system 10 in which themultiple subscriber units 14 compete for the allocation of wirelessresources.

Antenna devices 16 of corresponding subscriber units 14 can also operatein an omni-directional transmission mode in which information istransmitted in all or multiple directions from a corresponding antennaarray. More specifically, although lobe B shows a directional lobepattern for transmitting data, a new directional lobe setting isoptionally omni-directional or multi-directional. An omni-directional,multi-directional or narrowly-directional antenna setting can then becompared to any other type of antenna array setting as previouslydiscussed.

Notably, it can be advantageous in some applications to initiallytransmit information in the reverse link to base unit 18 based on anomni-directional antenna setting because it is not known in whichdirection to initially transmit information to base unit 18. Thereafter,an optimal directional antenna array setting on which to transmitinformation can be determined using the above-mentioned method. In thisway, a subscriber unit 14 initially transmitting information on a newreverse link channel can be set to transmit in an omni-directional modeuntil a more efficient or directional lobe is determined. Data can betransmitted in quadrants or the like until an optimal narrow beam widthantenna setting is determined.

It can be determined via the use of lobe compare bit 225 that theorientation or position of a subscriber unit's 14 corresponding antennadevice 16 changes frequently. In certain instances, an omni-directionalantenna setting may be the most efficient setting for establishing awireless link between a subscriber unit 14 and base unit 18.

An omni-directional antenna setting can also be advantageously used inhard hand-offs between one base unit 18 and another. For instance, asubscriber unit 14-1 can maintain a continuous connection with ahardwired network on the ground, but via a new base station at adifferent location.

While this invention has been particularly shown and described withreferences to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the scope of the inventionencompassed by the appended claims.

What is claimed is:
 1. A method comprising: monitoring wirelesstransmissions, at least two of which are based on different directionaltransmissions from a transmitter; generating a first type of feedbackmessages to control a power output level of the transmitter; generatinga second type of feedback messages to indicate which of the at least twodifferent directional transmissions from the transmitter supports ahigher quality received signal; communicating the first and second typeof feedback messages over a shared feedback channel to adjust settingsof the transmitter; partitioning the shared feedback channel intomultiple repeating sequences of frames; and communicating either a firstor second type of feedback message in a frame of the shared feedbackchannel depending on a position of the frame in a sequence ofperiodically repeating frames.
 2. The method as in claim 1 furthercomprising: in a first frame of the shared feedback channel,transmitting a first type of feedback message, and in a frame contiguouswith the first frame, transmitting a second type of feedback message. 3.The method as in claim 2, wherein at least one of the first type offeedback message or the second type of feedback message is a single bit.4. The method as in claim 2, wherein the first type of feedback messageis a power control bit.
 5. The method as in claim 2, wherein the secondtype of feedback message is a lobe control bit.
 6. The method as inclaim 1 further comprising: partitioning a data channel into frames inwhich data information is transmitted; and for two successive frames ofthe data channel, generating two different directional transmissionsfrom the transmitter.
 7. The method as in claim 6 further comprising:receiving a feedback message at the transmitter indicating which of thetwo different directional data transmissions results in a higher qualityreceived signal.
 8. A method comprising: monitoring wirelesstransmissions, at least two of which are based on different directionaltransmissions from a transmitter; generating a feedback message of afirst type to control a power output level of the transmitter;generating a feedback message of a second type to indicate which of theat least two different directional transmissions from the transmittersupports a higher quality received signal; and communicating thefeedback message of the first type and the feedback message of thesecond type over a feedback channel to adjust settings of thetransmitter, wherein the feedback channel is partitioned into arepeating sequence of frames; and each of the feedback messages iscommunicated in a frame of the repeating sequence of frames, wherein aposition of that frame in the repeating sequence of frames is used toidentify the type of each of the feedback messages.
 9. The method as inclaim 8 wherein the feedback channel is a shared feedback channel.